Skin care compositions comprising substituted diamines

ABSTRACT

Skin care compositions comprising certain substituted diamines, which are particularly beneficial for skin lightening and achieving evenness of color, especially for face and underarm skin.

TECHNICAL FIELD

The present invention relates to compositions for face and body skin.

BACKGROUND OF THE INVENTION

The desire to look young and healthy is universal. The primary attributes of the young and healthy-looking skin are evenness of the skin color and texture. Age spots and other skin hyperpigmentation are undesirable. In many parts of the world, consumers also want to lighten their background skin color. Accordingly, there is a need for commercially feasible, effective skin care compositions, especially skin lightening products.

Various compositions comprising some substituted diamines or related structures have been described, for example in EP 2193779 (Cognis); WO 2005/016895 (KIM); WO 2008/009860 (L'Oreal); Hirota et al., U.S. Pat. No. 4,412,943; EP 0653208 (Pfizer, Inc.); Dowell et al., U.S. Pat. No. 5,393,519; Winchell et al., US 2001/0041170; Chassot et al., US 2003/0172471; DE 20110356 (Wella AG); Walton, US 2005/0220832; Wagner et al., US 2009/0010860; WO 2008/101692 (Beiersdorf AG); WO 2008/129188 (L'Oreal); EP 0922 447 (Beiersdorf AG).

SUMMARY OF THE INVENTION

The present invention is based at least in part on the finding that among hundreds of compounds described as “substituted diamines,” a sub-group (Structure I below) with critical structural elements, is effective at inhibiting melanin production.

The invention includes skin care compositions, preferably skin lightening compositions, comprising substituted diamines of Structure I. The invention also includes methods of using such compositions for skin care, especially face and underarms, most especially for skin lightening.

DETAILED DESCRIPTION OF THE INVENTION

Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word “about.” All amounts are by weight of the final composition, unless otherwise specified.

It should be noted that in specifying any range of concentration or amount, any particular upper concentration can be associated with any particular lower concentration or amount.

For the avoidance of doubt, the word “comprising” is intended to mean “including” but not necessarily “consisting of” or “composed of.” In other words, the listed steps or options need not be exhaustive.

The disclosure of the invention as found herein is to be considered to cover all embodiments as found in the claims as being multiply dependent upon each other irrespective of the fact that claims may be found without multiple dependency or redundancy.

“Skin Care Composition” as used herein, is meant to include a composition for topical application to skin of mammals, especially humans. Such a composition may be generally classified as leave-on or rinse off, and includes any product applied to a human body for improving appearance, cleansing, odor control or general aesthetics. The composition of the present invention can be in the form of a liquid, lotion, cream, foam, scrub, gel, soap bar or toner, or applied with an implement or via a face mask, pad or patch. Non-limiting examples of skin care compositions include leave-on skin lotions and creams, shampoos, conditioners, shower gels, toilet bars, antiperspirants, deodorants, dental products, shave creams, depilatories, lipsticks, foundations, mascara, sunless tanners and sunscreen lotions. “Skin” as used herein is meant to include skin on the face and body (e.g., neck, chest, back, arms, underarms, hands, legs, buttocks and scalp). The inventive compositions are especially useful for application to skin areas with the highest incidence of hyperpigmentation—face and underarms, most preferably the inventive compositions are skin lightening compositions, deodorants and anti-perspirants.

“Lightening” as used herein, means the lightening of skin color as well as the lightening of spots (hyperpigmentation) on the skin, like age spots and freckles.

Substituted Diamines

The inventive compositions include substituted diamines of Structure I:

wherein R₁ and R₂ are independently selected from the group consisting of cyclohexyl, phenyl, naphthyl, ortho-, meta- or para-substituted phenyl with the following substituents: C₁-C₅ alkyl, C₁-C₅ alkoxy, halogens (F, Cl, Br), trifluoromethyl;

a is 2 or 3; and R₃ and R₄ are independently selected from the group consisting of methyl, ethyl, fused to form pyrrolidino, piperidino or morpholino group. Preferably, to achieve improved inhibition of melanin production, “a” is 2, R₁ and R₂ are independently selected from the group consisting of cyclohexyl, phenyl, naphthyl, ortho-, meta- or para-substituted phenyl with the following substituents: C₁-C₅ alkyl, C₁-C₅ alkoxy, halogens (F, Cl, Br), trifluoromethyl; R₃ and R₄ are independently selected from methyl or ethyl, fused to form pyrrolidino. Even more preferably, R₁ and R₂ are the same or different and are selected from ortho-, meta- or para-substituted phenyl, substituted with hydrogen, methyl, methoxy, Cl, F, CF₃, or fused phenyl; and R₃ and R₄ are both independently selected from methyl or ethyl.

It will be understood that Structure I encompasses amine salts (e.g., halogen salts, tosylates, mesylates, carboxylates, and hydroxides).

Amounts of the substituted diamines may range from 0.001% to 20%, preferably from 0.01 to 10%, more preferably from 0.1 to about 10%, optimally from 0.1 to about 5% by weight of the composition.

Process of Making Substituted Diamines

Reagents & Analytical Methods

All reagents and solvents were obtained from commercial sources (Sigma-Aldrich, EMD Chemicals) and used without further purification unless otherwise indicated. Parallel reactions and parallel solvent removal were performed using a Buchi Syncore reactor (Buchi Corporation, New Castle, Del.). Reaction monitoring was performed using either thin layer chromatography (TLC) or gas chromatography (GC). TLC was performed using silica gel 60 F₂₅₄ plates (EMD Chemicals) and visualizing by UV (254 nm), 4% phosphomolybdic acid (PMA) in ethanol (EtOH), 4% ninhydrin in ethanol and/or using an iodine chamber. GC was performed on a Hewlett Packard 5890 Series II Plus Gas Chromatograph equipped with a HP-1 crosslinked methyl silicone gum (25 m×0.2 mm×0.33 mm film thickness) column operated by GC Chemstation (HP, version A.06.01 [403], Hewlett Packard) software and the following parameters and gradient applied; injector temp 250° C., oven temp: 70° C. (2 min), ramp at 25° C./min up to 250° C., held at 250° C. (11 min). High performance liquid chromatography (HPLC) was performed using a Waters 2695 Separations Module equipped with a Waters 2996 Photodiode Array Detector and operated with Empower Pro software (Waters Corp.). Separations were carried out at 1 ml/min on a Restek Pinnacle DB C18 column (5 um, 4.6×150 mm) maintained at 30° C. Samples for HPLC were prepared by dissolving 1 mg of sample in 1 ml mobile phase A:B (1:1) and injecting 5 μL onto the column. The mobile phase consisted of A=0.1% trifluoroacetic acid (TFA) in water and B=0.1% TFA in acetonitrile (ACN) operated using gradient elution from 95:5 A:B to 5:95 A:B (gradient, 25 min) followed by 100% B (isocratic, 5 min). Liquid chromatography/mass spectrometry (LC-MS) was performed using a Finnigan Mat LCQ Mass Spectrometer via direct infusion of samples (50 ppm) in methanol and the total ion count monitored using electrospray ionization in the (+) mode (ESI+). ¹H and ¹³C Nuclear magnetic resonance (NMR) spectroscopy was performed using a Eft-60 NMR Spectrometer (Anasazi instruments, Inc.) and processed using WinNuts software (Acorn NMR, Inc.). Melting points were determined using a Meltemp apparatus (Laboratory Devices). Purity was determined by HPLC-UV/Vis or GC.

LC-MS Structure Purity (% Relative ID Chemical Name R₁ (%) Abundance) 3a N-benzyl-N-(cyclohexylmethyl)-N′,N′- cyclohexyl 99.9 275 (100) dimethylethane-1,2-diamine 3b N,N-dibenzyl-N′,N′-dimethylethane-1,2-diamine phenyl 99.5 269 (100) 3c N-benzyl-N′,N′-dimethyl-N-(2-phenylethyl)ethane- benzyl 99.9 283 (100) 1,2-diamine 3d N-benzyl-N′,N′-dimethyl-N-(naphthalen-2- 2-naphthyl 99.9 319 (100) ylmethyl)ethane-1,2-diamine 3e N-benzyl-N′,N′-dimethyl-N-(2- 2-methylphenyl 99.9 283 (100) methylbenzyl)ethane-1,2-diamine 3f N-benzyl-N′,N′-dimethyl-N-(3- 3-methylphenyl 99.9 283 (100) methylbenzyl)ethane-1,2-diamine 3g N-benzyl-N′,N′-dimethyl-N-(4- 4-methylphenyl 99.9 283 (100) methylbenzyl)ethane-1,2-diamine 3h N-benzyl-N-(4-methoxybenzyl)-N′,N′- 4-methoxyphenyl 99.9 299 (100) dimethylethane-1,2-diamine 3i N-benzyl-N-(4-fluorobenzyl)-N′,N′-dimethylethane- 4-fluorophenyl 99.9 287 (100) 1,2-diamine

Aldehydes 1 (1.2 equivalents) were added to mixtures of polystyrene cyanoborohydride resin (PS-BH₃CN) (2 equivalents) in 1,2-dichloroethylene (DCE) (4 ml), followed by N′-Benzyl-N,N-dimethylethylenediamine 2 (217 ul, 1 equivalent) and glacial acetic acid (AcOH) (400 ul) and the mixtures stirred in sealed vessels at R.T. for 16 h. The reactions were monitored by TLC using 10% methanol in chloroform (CHCl₃) and PMA staining until complete disappearance of the aldehydes. The solids were filtered off and washed with 15% isopropanol (IPA) in CHCl₃ (2×3 ml). The combined organic layers were washed with 2M K₂CO₃: saturated NaCl (1:1) (7 ml), dried with Na₂SO₄ and the solvents removed in parallel under reduced pressure. The crude products were purified by flash chromatography on silica gel using the following (MeOH:CHCl₃) compositions: 3a, 3h (9:91); 3b, 3c, 3d, 3e, 3f, 3g, 3i (8:92). Product purity was determined by GC and product identity confirmed by LC-MS (ESI+) and/or ¹H NMR.

General Procedure II: Synthesis of Substituted Diamines (5)

LC-MS Structure Purity (% Relative ID Chemical Name R₁ R₂ R₃ n (%) Abundance) 5a N,N-bis(cyclohexylmethyl)-N′,N′- cyclohexyl methyl methyl 2 99.9 281 (100) dimethylethane-1,2-diamine 5b N,N-bis(4-methoxybenzyl)-N′,N′- 4-methoxyphenyl methyl methyl 2 99.9 329 (100) dimethylethane-1,2-diamine 5c N,N-bis(4-fluorobenzyl)-N′,N′- 4-fluorophenyl methyl methyl 2 99.9 305 (100) dimethylethane-1,2-diamine 5d N,N-dibenzyl-N′,N′-diethylethane- phenyl ethyl ethyl 2 99.9 297 (100) 1,2-diamine 5e N,N-dibenzyl-2-(pyrrolidin-1- phenyl pyrrolidino 2 99.9 295 (100) yl)ethanamine 5f N,N-dibenzyl-N′,N′- phenyl methyl methyl 3 99.9 283 (100) dimethylpropane-1,3-diamine

Aldehydes 1 (2.4 equivalents) were added to mixtures of polystyrene cyanoborohydride resin (4 equivalents) in 1,2-dichloroethylene (DCE) (4.5 ml), followed by diamines 4 (1 equivalent) and glacial acetic acid (AcOH) (450 ul) and the mixtures stirred in sealed vessels at R.T. for 16 h. The reactions were monitored by TLC using 10% methanol in chloroform (CHCl₃) and PMA staining until complete disappearance of the aldehydes. The solids were filtered off and washed with (DCE) (5 ml). The combined organic layers were washed with 2M K₂CO₃ (5 ml), dried with Na₂SO₄ and the solvents removed under reduced pressure. The crude products were purified by flash chromatography on silica gel using the following (MeOH:CHCl₃) compositions: 5a, 5c, 5e, 5f (8:92); 5b, 5d (9:91). Product purity was determined by GC and product identity confirmed by LC-MS (ESI+) and/or ¹H NMR.

Specific Procedures: Synthesis of Miscellaneous Compounds

N-benzyl-N-[2-(dimethylamino)ethyl]benzamide (7)-Benzoyl chloride 6 (128 ul, 1.09 mmol) was added to a mixture of N′-Benzyl-N,N-dimethylethylenediamine 2 (163 ul, 0.84 mmol) and polystyrene di-isopropylamine (PS-DIPA) (210 mg, 0.94 mmol) in ACN (3 ml) and the mixture stirred at R.T. for 1 h. At this time, TLC (10% methanol in chloroform) showed the formation of a major product and traces of starting amine. The solution was diluted with ethyl ether (10 ml), washed with 0.5 N NaOH (5 ml), dried with Na₂SO₄ and the solvents removed to give an oil. The crude product was purified by flash chromatography using 6% methanol in chloroform. Identification of the desired product [m/z [M+H]⁺ 283 (100%)] was confirmed by LC-MS analysis (ESI+) and purity (99.9%) was confirmed by GC analysis.

N-benzyl-N-ethyl-N′,N′-dimethylethane-1,2-diamine (3j)-Benzaldehyde 8 (144 ul, 1.41 mmol) was added to a mixture of polystyrene cyanoborohydride resin (1.08 g, 2.72 mmol) in 1,2-dichloroethylene (DCE) (3.5 ml), followed by N,N-dimethyl-N′-ethylethylenediamine 9 (171 ul, 1.09 mmol) and glacial acetic acid (AcOH) (350 ul) and the mixture stirred in a sealed vessel at RT. for 16 h. At this time, TLC (10% methanol in chloroform) showed the clean formation of product and the complete disappearance of benzaldehyde. The solids were filtered off and washed with (DCE) (5 ml). The combined organic layers were washed with 2M K₂CO₃ (5 ml), dried with Na₂SO₄ and the solvents removed under reduced pressure to give an oil. The crude product was purified by flash chromatography using 8% methanol in chloroform. Identification of the desired product [m/z [M+H]⁺ 207 (100%)] was confirmed by LC-MS analysis (ESI+) and purity (99.9%) was confirmed by GC analysis.

N-benzyl-N′,N′-dimethyl-N-(1-phenylethyl)ethane-1,2-diamine (11)-Acetophenone 10 (158 ul, 1.35 mmol) was added to a mixture of polystyrene cyanoborohydride resin (898 g, 2.24 mmol) in 1,2-dichloroethylene (DCE) (4 ml), followed by N′-Benzyl-N,N-dimethylethylenediamine 2 (217 ul, 1.12 mmol) and glacial acetic acid (AcOH) (400 ul) and the mixture stirred in a sealed vessel at R.T. for 16 h. At this time, TLC (10% methanol in chloroform) showed the clean formation of product and the complete disappearance of acetophenone. The solids were filtered off and washed with (DCE) (5 ml). The combined organic layers were washed with 2M K₂CO₃ (5 ml), dried with Na₂SO₄ and the solvents removed under reduced pressure to give an oil. The crude product was purified by flash chromatography using 8% methanol in chloroform. Identification of the desired product [m/z [M+H]⁺ 283 (100%)] was confirmed by LC-MS analysis (ESI+) and purity (95.1%) was confirmed by GC analysis.

Skin Care Compositions

Compositions of this invention also include a cosmetically acceptable carrier. Amounts of the carrier may range from about 1 to about 99.9%, preferably from about 70 to about 95%, optimally from about 80 to about 90% by weight of the composition. Among the useful carriers are water, emollients, fatty acids, fatty alcohols, humectants, thickeners and combinations thereof. The carrier may be aqueous, anhydrous or an emulsion. Preferably the compositions are aqueous, especially water and oil emulsions of the W/O or O/W or triplex W/O/W variety. Water when present may be in amounts ranging from about 5 to about 95%, preferably from about 20 to about 70%, optimally from about 35 to about 60% by weight.

Emollient materials may serve as cosmetically acceptable carriers. These may be in the form of silicone oils, synthetic esters and hydrocarbons. Amounts of the emollients may range anywhere from about 0.1 to about 95%, preferably between about 1 and about 50% by weight of the composition.

Silicone oils may be divided into the volatile and nonvolatile variety. The term “volatile” as used herein refers to those materials which have a measurable vapor pressure at ambient temperature. Volatile silicone oils are preferably chosen from cyclic (cyclomethicone) or linear polydimethylsiloxanes containing from 3 to 9, preferably from 4 to 5, silicon atoms.

Nonvolatile silicone oils useful as an emollient material include polyalkyl siloxanes, polyalkylaryl siloxanes and polyether siloxane copolymers. The essentially nonvolatile polyalkyl siloxanes useful herein include, for example, polydimethyl siloxanes with viscosities of from about 5×10⁻⁶ to 0.1 m²/s at 25° C. Among the preferred nonvolatile emollients useful in the present compositions are the polydimethyl siloxanes having viscosities from about 1×10⁻⁵ to about 4×10⁻⁴ m²/s at 25° C.

Another class of nonvolatile silicones are emulsifying and non-emulsifying silicone elastomers. Representative of this category is Dimethicone/Vinyl Dimethicone Crosspolymer available as Dow Corning 9040, General Electric SFE 839, and Shin-Etsu KSG-18. Silicone waxes such as Silwax WS-L (Dimethicone Copolyol Laurate) may also be useful.

Among the ester emollients are:

1) Alkyl esters of saturated fatty acids having 10 to 24 carbon atoms. Examples thereof include behenyl neopentanoate, isononyl isonanonoate, isopropyl myristate and octyl stearate.

2) Ether-esters such as fatty acid esters of ethoxylated saturated fatty alcohols.

3) Polyhydric alcohol esters. Ethylene glycol mono and di-fatty acid esters, diethylene glycol mono- and di-fatty acid esters, polyethylene glycol (200-6000) mono- and di-fatty acid esters, propylene glycol mono- and di-fatty acid esters, polypropylene glycol 2000 monostearate, ethoxylated propylene glycol monostearate, glyceryl mono- and di-fatty acid esters, polyglycerol poly-fatty esters, ethoxylated glyceryl mono-stearate, 1,3-butylene glycol monostearate, 1,3-butylene glycol distearate, polyoxyethylene polyol fatty acid ester, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters are satisfactory polyhydric alcohol esters. Particularly useful are pentaerythritol, trimethylolpropane and neopentyl glycol esters of C₁-C₃₀ alcohols.

4) Wax esters such as beeswax, spermaceti wax and tribehenin wax.

5) Sugar ester of fatty acids such as sucrose polybehenate and sucrose polycottonseedate.

Hydrocarbons which are suitable cosmetically acceptable carriers include petrolatum, mineral oil, C₁₁-C₁₃ isoparaffins, and especially isohexadecane, available commercially as Permethyl 101A from Presperse Inc.

Fatty acids having from 10 to 30 carbon atoms may also be suitable as cosmetically acceptable carriers. Illustrative of this category are pelargonic, lauric, myristic, palmitic, stearic, isostearic, oleic, hydroxystearic and behenic acids.

Fatty alcohols having from 10 to 30 carbon atoms are another useful category of cosmetically acceptable carrier. Illustrative of this category are stearyl alcohol, lauryl alcohol, myristyl alcohol and cetyl alcohol.

Humectants of the polyhydric alcohol-type can be employed as cosmetically acceptable carriers. Typical polyhydric alcohols include glycerol, polyalkylene glycols and more preferably alkylene polyols and their derivatives, including propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol and derivatives thereof, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1,3-butylene glycol, isoprene glycol, 1,2,6-hexanetriol, ethoxylated glycerol, propoxylated glycerol and mixtures thereof. The amount of humectant may range anywhere from 0.5 to 50%, preferably between 1 and 15% by weight of the composition.

Thickeners can be utilized as part of the cosmetically acceptable carrier of compositions according to the present invention. Typical thickeners include crosslinked acrylates (e.g. Carbopol 982®), hydrophobically-modified acrylates (e.g. Carbopol 1382®), cellulosic derivatives and natural gums. Among useful cellulosic derivatives are sodium carboxymethylcellulose, hydroxypropyl methocellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, ethyl cellulose and hydroxymethyl cellulose. Natural gums suitable for the present invention include guar, xanthan, sclerotium, carrageenan, pectin and combinations of these gums. Inorganics may also be utilized as thickeners, particularly clays such as bentonites and hectorites, fumed silicas, and silicates such as magnesium aluminum silicate (Veegum®). Amounts of the thickener may range from 0.0001 to 10%, usually from 0.001 to 1%, optimally from 0.01 to 0.5% by weight of the composition.

Optional Ingredients

The inventive composition preferably includes an additional skin lightening compound, to obtain optimum skin lightening performance at an optimum cost. Illustrative substances are placental extract, lactic acid, niacinamide, arbutin, kojic acid, ferulic acid, hydroquinone, resorcinol and derivatives including 4-substituted resorcinols and combinations thereof. More preferably, such additional skin lightening compound is a tyrosinase inhibitor, to complement the melanogenesis inhibition activity of the substituted monoamines, most preferably a compound selected from the group consisting of kojic acid, hydroquinone and 4-substituted resorcinol. Amounts of these agents may range from about 0.1 to about 10%, preferably from about 0.5 to about 2% by weight of the composition. It is preferred that the skin lightening coactive according to the invention is vitamin B3 or a derivative thereof and is selected from the group consisting of niacinamide, nicotinic acid esters, non-vasodilating esters of nicotinic acid, nicotinyl amino acids, nicotinyl alcohol esters of carboxylic acids, nicotinic acid N-oxide, niacinamide N-oxide and mixtures thereof.

Sunscreen is another preferred ingredient of the inventive compositions Particularly preferred are such materials as ethylhexyl p-methoxycinnamate (available as Parsol MCX®), Avobenzene (available as Parsol 1789®), octylsalicylate (available as Dermablock OS®), tetraphthalylidene dicamphor sulfonic acid (available as Mexoryl SX®), benzophenone-4 and benzophenone-3 (Oxybenzone). Inorganic sunscreen actives may be employed such as microfine titanium dioxide, zinc oxide, polyethylene and various other polymers. By the term “microfine” is meant particles of average size ranging from about 10 to about 200 nm, preferably from about 20 to about 100 nm. Amounts of the sunscreen agents when present may generally range from 0.1 to 30%, preferably from 2 to 20%, optimally from 4 to 10% by weight of the composition.

More preferred inventive compositions include both the additional skin lightening compound, especially tyrosinase inhibitor, and a sunscreen compound.

Another preferred ingredient of the inventive compositions is a retinoid. As used herein, “retinoid” includes all natural and/or synthetic analogs of Vitamin A or retinol-like compounds which possess the biological activity of Vitamin A in the skin as well as the geometric isomers and stereoisomers of these compounds. The retinoid is preferably retinol, retinol esters (e.g., C2-C22 alkyl esters of retinol, including retinyl palmitate, retinyl acetate, retinyl propionate), retinal, and/or retinoic acid (including all-trans retinoic acid and/or 13-cis-retinoic acid), more preferably retinoids other than retinoic acid. These compounds are well known in the art and are commercially available from a number of sources, e.g., Sigma Chemical Company (St. Louis, Mo.), and Boerhinger Mannheim (Indianapolis, Ind.). Other retinoids which are useful herein are described in U.S. Pat. Nos. 4,677,120, issued Jun. 30, 1987 to Parish et al.; U.S. Pat. No. 4,885,311, issued Dec. 5, 1989 to Parish et al.; U.S. Pat. No. 5,049,584, issued Sep. 17, 1991 to Purcell et al.; U.S. Pat. No. 5,124,356, issued Jun. 23, 1992 to Purcell et al.; and U.S. Pat. No. Reissue 34,075, issued Sep. 22, 1992 to Purcell et al. Other suitable retinoids are tocopheryl-retinoate [tocopherol ester of retinoic acid (trans- or cis-), adapalene {6-[3-(1-adamantyl)-4-methoxyphenyl]-2-naphthoic acid}, and tazarotene (ethyl 6-[2-(4,4-dimethylthiochroman-6-yl)-ethynyl]nicotinate). Preferred retinoids are retinol, retinyl palmitate, retinyl acetate, retinyl propionate, retinal and combinations thereof. The retinoid is preferably substantially pure, more preferably essentially pure. The compositions of this invention may contain a safe and effective amount of the retinoid, such that the resultant composition is safe and effective for regulating keratinous tissue condition, preferably for regulating visible and/or tactile discontinuities in skin, more preferably for regulating signs of skin aging, even more preferably for regulating visible and/or tactile discontinuities in skin texture associated with skin aging. The compositions preferably contain from or about 0.005% to or about 2%, more preferably 0.01% to or about 2%, retinoid. Retinol is preferably used in an amount of from or about 0.01% to or about 0.15%; retinol esters are preferably used in an amount of from or about 0.01% to or about 2% (e.g., about 1%); retinoic acids are preferably used in an amount of from or about 0.01% to or about 0.25%; tocopheryl-retinoate, adapalene, and tazarotene are preferably used in an amount of from or about 0.01% to or about 2%.

Surfactants may also be present in compositions of the present invention. Total concentration of the surfactant when present may range from about 0.1 to about 40%, preferably from about 1 to about 20%, optimally from about 1 to about 5% by weight of the composition. The surfactant may be selected from the group consisting of anionic, nonionic, cationic and amphoteric actives. Particularly preferred nonionic surfactants are those with a C₁₀-C₂₀ fatty alcohol or acid hydrophobe condensed with from 2 to 100 moles of ethylene oxide or propylene oxide per mole of hydrophobe; C₂-C₁₀ alkyl phenols condensed with from 2 to 20 moles of alkylene oxide; mono- and di-fatty acid esters of ethylene glycol; fatty acid monoglyceride; sorbitan, mono- and di-C₈-C₂₀ fatty acids; and polyoxyethylene sorbitan as well as combinations thereof. Alkyl polyglycosides and saccharide fatty amides (e.g. methyl gluconamides) are also suitable nonionic surfactants.

Preferred anionic surfactants include soap, alkyl ether sulfates and sulfonates, alkyl sulfates and sulfonates, alkylbenzene sulfonates, alkyl and dialkyl sulfosuccinates, C₈-C₂₀ acyl isethionate, C₈-C20 alkyl ether phosphates, C₈-C₂₀ sarcosinates and combinations thereof.

Preservatives can desirably be incorporated into the cosmetic compositions of this invention to protect against the growth of potentially harmful microorganisms. Suitable traditional preservatives for compositions of this invention are alkyl esters of para-hydroxybenzoic acid. Other preservatives which have more recently come into use include hydantoin derivatives, propionate salts, and a variety of quaternary ammonium compounds. Cosmetic chemists are familiar with appropriate preservatives and routinely choose them to satisfy the preservative challenge test and to provide product stability. Particularly preferred preservatives are phenoxyethanol, methyl paraben, propyl paraben, imidazolidinyl urea, sodium dehydroacetate and benzyl alcohol. The preservatives should be selected having regard for the use of the composition and possible incompatibilities between the preservatives and other ingredients in the emulsion. Preservatives are preferably employed in amounts ranging from 0.01% to 2% by weight of the composition.

Compositions of the present invention may include vitamins. Illustrative vitamins are Vitamin A (retinol), Vitamin B₂, Vitamin B₃ (niacinamide), Vitamin B₆, Vitamin B12, Vitamin C, Vitamin D, Vitamin E, Vitamin K and Biotin. Derivatives of the vitamins may also be employed. For instance, Vitamin C derivatives include ascorbyl tetraisopalmitate, magnesium ascorbyl phosphate and ascorbyl glycoside. Derivatives of Vitamin E include tocopheryl acetate, tocopheryl palmitate and tocopheryl linoleate. DL-panthenol and derivatives may also be employed. A particularly suitable Vitamin B₆ derivative is Pyridoxine Palmitate. Flavonoids may also be useful, particularly glucosyl hesperidin, rutin, and soy isoflavones (including genistein, daidzein, equol, and their glucosyl derivatives) and mixtures thereof. Total amount of vitamins or flavonoids when present may range from 0.0001 to 10%, preferably from 0.01% to 1%, optimally from 0.1 to 0.5% by weight of the composition.

Another type of useful substance can be that of an enzyme such as oxidases, proteases, lipases and combinations. Particularly preferred is superoxide dismutase, commercially available as Biocell SOD from the Brooks Company, USA.

Desquamation promoters may be present. Illustrative are the monocarboxylic acids. Monocarboxylic acids may be substituted or unsubstituted with a carbon chain length of up to 16. Particularly preferred carboxylic acids are the alpha-hydroxycarboxylic acids, beta-hydroxycarboxylic or polyhydroxycarboxylic acids. The term “acid” is meant to include not only the free acid but also salts and C₁-C₃₀ alkyl or aryl esters thereof and lactones generated from removal of water to form cyclic or linear lactone structures. Representative acids are glycolic, lactic malic and tartaric acids. A representative salt that is particularly preferred is ammonium lactate Salicylic acid is representative of the beta-hydroxycarboxylic acids. Amounts of these materials when present may range from about 0.01 to about 15% by weight of the composition. Other phenolic acids include ferulic acid, salicylic acid, kojic acid and their salts.

Dicarboxylic acids represented by the formula HOOC—(CxHy)-COOH where x=4 to 20 and y=6 to 40 such as azelaic acid, sebacic acid, oxalic acid, succinic acid, fumaric acid, octadecenedioic acid or their salts or a mixture thereof.

A variety of herbal extracts may optionally be included in compositions of this invention. Illustrative are pomegranate, white birch (Betula Alba), green tea, chamomile, licorice and extract combinations thereof. The extracts may either be water soluble or water-insoluble carried in a solvent which respectively is hydrophilic or hydrophobic. Water and ethanol are the preferred extract solvents.

Also included may be such materials as resveratrol, alpha-lipoic acid, ellagic acid, kinetin, retinoxytrimethylsilane (available from Clariant Corp. under the Silcare 1M-75 trademark), dehydroepiandrosterone (DHEA) and combinations thereof. Ceramides (including Ceramide 1, Ceramide 3, Ceramide 3B, Ceramide 6 and Ceramide 7) as well as pseudoceramides may also be utilized for many compositions of the present invention but may also be excluded. Amounts of these materials may range from about 0.000001 to about 10%, preferably from about 0.0001 to about 1% by weight of the composition.

Colorants, opacifiers and abrasives may also be included in compositions of the present invention. Each of these substances may range from about 0.05 to about 5%, preferably between 0.1 and 3% by weight of the composition.

The compositions of the present invention may contain a safe and effective amount of a peptide active selected from pentapeptides, derivatives of pentapeptides, and mixtures thereof. As used herein, “pentapeptides” refers to both the naturally occurring pentapeptides and synthesized pentapeptides. Also useful herein are naturally occurring and commercially available compositions that contain pentapeptides. A preferred commercially available pentapeptide derivative-containing composition is Matrixyl.RTM., which is commercially available from Sederma, France. The pentapeptides and/or pentapeptide derivatives are preferably included in amounts of from about 0.000001% to about 10%, more preferably from about 0.000001% to about 0.1%, even more preferably from about 0.00001% to about 0.01%, by weight of the composition. In embodiments wherein the pentapeptide-containing composition, Matrixyl.RTM, is used, the resulting composition preferably contains from about 0.01% to about 50%, more preferably from about 0.05% to about 20%, and even more preferably from about 0.1% to about 10%, by weight of the resulting composition, of Matrixyl.RTM.

Additional peptides, including but not limited to, di-, tri-, and tetrapeptides and derivatives thereof, and poly amino acid sequences of molecular weight from 200-20000. Amino acids may be naturally occurring or synthetic, dextro or levo, straight chain or cyclized and may be included in the compositions of the present invention in amounts that are safe and effective. As used herein, “peptides” refers to both the naturally occurring peptides and synthesized peptides. Also useful herein are naturally occurring and commercially available compositions that contain peptides.

Suitable dipeptides for use herein include Carnosine. Preferred tripeptides and derivatives thereof may be purchased as Biopeptide CL.RTM. and a copper derivative sold commercially as lamin, from Sigma (St. Louis, Mo.).

Skin moisturizers, e,g. hyaluronic acid and/or its precursor N-acetyl glucosamine may be included. N-acetyl glucosamine may be found in shark cartilage or shitake mushrooms and are available commercially from Maypro Industries, Inc (New York).

Anti-perspirants/deodorants skin care products of the invention may further include well known antiperspirant metal salts of aluminum, zinc, zirconium and zirconium aluminum mixtures of sulfates, chlorides, chlorohydroxides, tetrachlorohydrex glycinates, alums, formates, lactates, benzyl sulfonates, succinates, phenol sulfonates and the like. Typical levels of antiperspirant/deodorant agent are from about 0% to about 35%, preferably from about 0% to about 25% by weight of the composition. The composition may further include a complexing agent such as an organic acid or derivative thereof that are capable of forming complexes with the antiperspirant metallic salt. Examples of such complexing agents include, but are not limited to acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, tartaric acid, glycine and the like together with their cosmetically acceptable salts. Typical levels of complexing agent are from about 0% to about 15%, preferably from about 0% to about 10%, by weight of the composition.

The composition of the invention may comprise a conventional deodorant base as the cosmetically acceptable carrier. By a deodorant is meant a product in the stick, roll-on, or propellant medium which is used for personal deodorant benefit e.g. application in the under-arm area which may or may not contain anti-perspirant actives.

Deodorant compositions can generally be in the form of firm solids, soft solids, gels, creams, and liquids and are dispensed using applicators appropriate to the physical characteristics of the composition.

Deodorant compositions which are delivered through roll-ons generally comprise a liquid carrier. Such liquid carrier can be hydrophobic or comprise a mixture of both hydrophilic and hydrophobic liquids. They may be in the form of an emulsion or a microemulsion. The liquid carrier or mixture of carriers often constitutes from 30 to 95% by weight of the composition and in many instances from 40 to 80%.

Hydrophobic liquid carriers commonly can comprise one or more materials selected within the chemical classes of siloxanes, hydrocarbons, branched aliphatic alcohols, esters and ethers that have a melting point not higher than 25° C. and a boiling point of at least 100° C.

Hydrophilic carrier liquids that can be employed in compositions herein commonly comprise water and/or a mono or polyhydric alcohol or water-miscible homologue. Monohydric alcohols often are short chain, by which is meant that they contain up to 6 carbons, and in practice are most often ethanol or sometimes iso-propanol. Polyhydric alcohols commonly comprise ethylene or propylene glycol, or a homologue can be employed such as diethylene glycol.

The compositions that remain in liquid form can be applied employing conventional applicators such as a roll-on or by being pumped or squeezed through a spray-generating orifice. Such compositions may be thickened, for example using one or more thickeners described subsequently herein.

Compositions that are firm solids, commonly obtained by use of a gellant or structurant, can be applied employing a stick applicator and soft solids, gels and creams can be applied employing an applicator having a dispensing head provided with at least one aperture through which the soft solid, gel or cream can be extruded under mild pressure.

Suitable thickeners or gellants that may be used for achieving this is by use of water-soluble or dispersible materials of higher viscosity, including various of the emulsifiers, and/or thickened or gelled with water-soluble or water-dispersible polymers including polyacrylates, and water-soluble or dispersible natural polymers, such as water-soluble polysaccharide or starch derivatives, such as alginates, carageenan, agarose and water-dispersible polymers include cellulose derivatives.

The concentration of such polymers in the water-immiscible liquid is often selected in the range of from 1 to 20%, depending on the extent of thickening or structuring required, and the effectiveness of the chosen polymer in the liquid/mixture.

One class of structurant which is desirable by virtue of its long standing proven capability to produce firm solids and more recently in making soft solids, comprises waxes. Herein, the term wax is employed to encompass not only materials of natural origin that are solid with a waxy feel and water-insoluble at 30-40° C., but melt at a somewhat higher temperature, typically between 50 and 95° C., such as beeswax, candelilla or carnauba wax, but also materials having similar properties. Such other waxes include hydrocarbon waxes, e.g. paraffin wax, mineral wax and microcrystalline wax; synthetic waxes, such as polyethylene of 2000 to 10000 daltons; waxy derivatives or waxy components of natural waxes

Mixtures of materials within each class of gellant/structurant can be employed.

When the antiperspirant composition employed herein comprises an aerosol composition, it contains a propellant in addition to a base composition as described herein above, commonly in a weight ratio of from 95:5 to 40:60, and in many formulations, the weight ratio is from 90:10 to 50:50.

The propellant is conveniently a low boiling point material, typically boiling below −5° C., for example an alkane such as propane, butane or isobutane, and possibly containing a fraction of pentane or isopentane, or a hydrofluorocarbon or fluorocarbon of similar carbon content. During filling of the aerosol canister, the propellant gas is liquified by virtue of the elevated pressure that is generated therein.

Examples of a hardening agent useful in the skin care compositions of the present invention include, but are not limited to lower alkanol amines, diamines and amides wherein such materials comprise at least two lower alkanol groups, preferably from about two to about four lower alkanol groups having from about 2 to about 4 carbon atoms. Examples of such hardening agents include, but are not limited to tetrahydroxyalkyldiamine compounds such as tetrahydroxypropylethylenediamine, polyoxamine compounds such as polyoxyethylene, polyoxypropylene block copolymers of ethylenediamine and alkanolamide compounds such as coconut diethanolamide and lauryl monoethanolamide. Typical levels of hardening agent are from about 0% to about 5% by weight of the composition.

Further ingredients useful in skin care compositions herein may be selected from any and all: skin conditioning agents, skin feel mildness agents, suspending agents, auxiliary thickening agents, viscosity control agents, dispersants, solubilizing/clarifying agents, stabilizers, opacifiers/pearlescent agents, chelating/sequestering agents, hydrotropes, bactericides/fungicides, antioxidants, pH control agents, buffering agents, colorants and perfumes/fragrances, water, other optional ingredients (auxiliary agents) and the like.

The compositions of the present invention can also be optionally, incorporated into a water insoluble substrate for application to the skin such as in the form of a treated wipe.

While the above summarizes the present invention, it will become apparent to those skilled in the art that modifications, variations and alterations may be made without deviating from the scope and spirit of the present invention as described and claimed herein. The invention will now be further illustrated in the following non-limiting examples.

EXAMPLE 1

Various representative substituted diamines of Structure I within the scope of the invention were investigated for inhibition of melanogenesis activity.

Melanoderm tissue equivalent model MEL-300 (MatTek: Ashland, Mass.) containing melanocytes obtained from dark skin individuals were cultured as per supplier instructions. Components were added to the maintenance medium phase (no topical treatments) at a final concentration of 10 μM for 14 days at which time the experiment was terminated and the tissues assessed for melanin content. Medium and treatments were changed three times per week. DMSO was utilized as the vehicle control and all treatments were performed at least in duplicate.

For quantification of total melanin, each Melanoderm was placed into an individual Eppendorf tube (2 mL) into which 250 μL of Solvable™ tissue solubilizer (Packard Bioscience Co., Cat# 6NE9100) was added. Each tube was vortexed and incubated at 60° C. for 18 hours. Each sample was then centrifuged (5-minutes at 13,000 RPMs) to remove any particulates. 100 or 200 μL of supernatant were transferred to a 96 well microtiter plate and the absorbance read at 490 nm. Total melanin content was calculated from a standard curve using synthetic melanin (Sigma Cat# M8631). Data was analyzed for significance using the t-test in Microsoft Excel to generate p-values (p-values less than 0.01 represent 99% confidence, p values of 0.05 represent 95% confidence both of which are statistically significant).

The results that were obtained are summarized in Table 1. The results show that compounds included in this invention inhibit melanogenesis.

TABLE 1 Melanoderm (% Reduction Compound ID Structure at 10 μM) p value  3b

39.5 0.005  3a

51.3 0.0017  5b

48.7 0.0003  3h

48.8 0.0002  5d

45.6 0.0002  5a

42.5 0.0004  5f

50 0.0001  3c

51.8 0.0002 11

47.8 0.0002  3d

56 0.0001  3e

46.6 0.0004  3i

47.8 0.0002  5c

49.3 0.0018  3f

51.6 0.0003  3g

53.2 0.005  5e

40.6 0.0131

COMPARATIVE EXAMPLE 2

This example investigated structural criticalities of the compounds within the invention.

TABLE 2 Com- Melanoderm pound (% Reduction ID Structure at 10 μM) p value 7

4.4 0.0618 3j

−0.1 0.4514

It can be seen that Compound 3b in Table 1 (within the scope of the invention) is effective at melanogenesis inhibition, while Compound 7 in Table 2 (outside the scope of the invention) is not. This demonstrates the criticality of diamine functionality. It can also be seen that Compounds 3a and 3b in Table 1 (within the scope of the invention) is effective at melanogenesis inhibition, while Compound 3j in Table 2 (outside the scope of the invention) is not. This demonstrates the criticality of both R₁ and R₂ being cyclic substitutents.

EXAMPLE 3

The following skin lightening product is prepared according to the invention:

INGREDIENT % composition by weight Water q.s. to 100 Stearic acid 18.00 Cetyl alcohol 0.40 Glyceryl monostearate 0.60 Silicone oil 0.50 Sodium cetostearyl sulphate 1.0 Mixture of sorbitan esters and 1.5 ethoxylated fatty acid esters Alkyl acrylate cross polymer 0.15 Polyhydric alcohol 10.00 Preservatives 0.5 Niacinamide 1.00 Inventive compound 3b 2.00 Parsol MCX 0.4 Benzophenones 0.75 Titanium dioxide 0.6

EXAMPLE 4

Skin care products within the scope of the invention are prepared:

Component A B C D Disodium EDTA 0.100 0.100 0.100 01.00 Inventive Compound 3a 2.000 0 1 0 Inventive Compound 3b 0 2.000 0 1 Methyl sulfonyl methane 0 0 2.000 0 Niacinamide 4.000 4.000 4.000 5.000 Octadecenedioic acid 0 0 0 2.000 Isohexadecane 3.000 3.000 3.000 3.000 Isopropyl isostearate 1.330 1.330 1.330 1.330 Sucrose polycottonseedate 0.670 0.670 0.670 0.670 Polymethylsilsesquioxane 0.250 0.250 0.250 0.250 Cetearyl glucoside + cetearyl 0.200 0.200 0.200 0.200 alcohol Behenyl alcohol 0.400 0.400 0.400 0.400 Ethylparaben 0.200 0.200 0.200 0.200 Propylparaben 0.100 0.100 0.100 0.100 Cetyl alcohol 0.320 0.320 0.320 0.320 Stearyl alcohol 0.480 0.480 0.480 0.480 Tocopheryl acetate 0.500 0.500 0.500 0.500 PEG-100 stearate 0.100 0.100 0.100 0.100 Glycerin 7.000 7.000 7.000 10.000 Titanium dioxide 0.604 0.604 0.604 0.604 Polyacrylamide + C13-14 2.000 2.000 2.000 2.000 isoparaffin + laureth-7 Panethenol 1.000 1.000 1.000 1.000 Benzyl alcohol 0.400 0.400 0.400 0.400 Dimethicone + dimethiconol 2.000 2.000 2.000 2.000 Water [to 100 g] to 100 to 100 to 100 To 100 Total 100 100 100 100

The water phase ingredients were combined in a suitable vessel and heated to 75° C. In a separate suitable vessel, combine the oil phase ingredients and heat to 75° C. Next add the oil phase to the water phase and mill the resulting emulsion (e.g., with a Tekmar™ T-25 mill). Then, add the thickener to the emulsion and cool the emulsion to 45° C. while stirring. At 45° C., add the remaining ingredients. Cool the product and stir to 30° C. and pour into suitable containers. The compositions are chronically applied topically to areas of hyperpigmented skin.

EXAMPLE 5

A representative skin care composition of the present invention in the form of a cosmetic lotion is outlined below:

INGREDIENT WEIGHT % Water Balance Disodium EDTA 0.05 Methyl Paraben 0.15 Magnesium Aluminum Silicate 0.60 Triethanolamine 1.20 Inventive compound 5a 1.00 Xanthan Gum 0.20 Natrosol ® 250HHR (ethyl cellulose) 0.50 Butylene Glycol 3.00 Glycerin 2.00 Sodium Stearoyl Lactylate 0.10 Glycerol Monostearate 1.50 Stearyl Alcohol 1.50 Isostearyl Palmitate 3.00 Silicone Fluid 1.00 Cholesterol 0.25 Sorbitan Stearate 1.00 Butylated Hydroxy Toluene 0.05 Vitamin E Acetate 0.01 PEG-100 Stearate 2.00 Stearic Acid 3.00 Propyl Paraben 0.10 Parsol MCX ® 2.00 Caprylic/Capric Triglyceride 0.50 Hydroxycaprylic Acid 0.01 C12-15 Alkyl Octanoate 3.00 (Isotridecyloxy)propionic acid (branched) 2.00 or (Isotridecyloxy)acetic acid (branched) Vitamin A Palmitate 0.10 Bisabolol 0.01 Vitamin A Acetate 0.01 Fragrance (20% Limonene and 3% gamma 0.03 terpinene) Retinol 50C 0.02

EXAMPLE 6

A water-in-oil topical liquid make-up foundation according to invention is described:

INGREDIENT WEIGHT % (Isotridecyloxy)propionic acid (branched) 2.00 or (Isotridecyloxy)acetic acid (branched) Cyclomethicone 9.25 Oleyl Oleate 2.00 Dimethicone Copolyol 20.00 Talc 3.38 Pigment (Iron Oxides) 10.51 Spheron L-1500 (Silica) 0.50 Synthetic Wax Durachem 0602 0.10 Arachidyl Behenate 0.30 Cyclomethicone 1.00 Trihydroxystearin 0.30 Laureth-7 0.50 Propyl Paraben 0.25 Perfume 0.1 Water balance Inventive compound 5a 3.00 Methyl Paraben 0.12 Propylene Glycol 8.00 Niacinamide 4.00 Glycerin 3.00 Sodium Chloride 2.00 Sodium Dehydroacetate 0.30

EXAMPLE 7

An aerosol packaged foaming cleanser is outlined:

INGREDIENT WEIGHT % Sunflower Seed Oil 10.00 Glycerin 10.00 Maleated Soybean Oil 5.00 Silicone Urethane 1.00 Polyglycero-4 Oleate 1.00 Sodium C14-16 Olefin Sulfonate 15.00 Sodium Lauryl Ether Sulphate (25% active) 15.00 Cocoamidopropylbetaine 15.00 DC 1784 ® (Silicone Emulsion 50%) 5.00 Polyquaternium-11 1.00 Inventive compound 3a 1.00 Fragrance (20% Limonene) 1.00 Water Balance

EXAMPLE 8

A toilet bar illustrative of the present invention is outlined:

INGREDIENT WEIGHT % Sodium Soap (85/15 Tallow/Coconut) 77.77 Inventive compound 5a 3.50 Dimethicone 2.00 Sodium Chloride 0.77 Titanium Dioxide 0.40 Ethylene Brassylate 1.50 Disodium EDTA 0.02 Sodium Etidronate 0.02 Fluorescer 0.024 Water Balance

EXAMPLE 9

A shampoo composition useful in the context of the present invention is described:

INGREDIENT WEIGHT % Ammonium Laureth Sulfate 12.00 Ammonium Lauryl Sulfate 2.00 Cocoamidopropyl Betaine 2.00 Sodium Lauroamphoacetate 2.00 Glycerin 12.00 Inventive Compound 5d 5.50 Ethylene Glycol Distearate 1.50 Cocomonoethanolamide 0.80 Cetyl Alcohol 0.60 Polyquaternium-10 0.50 Dimethicone 1.00 Zinc Pyridinethione 1.00 Sodium Citrate 0.40 Citric Acid 0.39 Sodium Xylene Sulfonate 1.00 Fragrance (10% Limonene) 0.40 Sodium Benzoate 0.25 Kathon CG ® 0.0008 Benzyl Alcohol 0.0225 Water Balance

EXAMPLE 10

This Example illustrates an antiperspirant/deodorant formula incorporating the phenoxyalkylamine compound according to the present invention.

Ingredient Weight % (Isotridecyloxy)propionic acid (branched) 2.00 Cyclopentasiloxane 39 Dimethicone 20 Aluminum Zirconium Trichlorohydrex Glycinate 15 Inventive Compound 5a 5.0 C18-C36 Acid Triglyceride 5.0 Microcrystalline Wax 3.0 Glycerin 8.0 Silica 2.5 Dimethicone Crosspolymer 1.0 Ethylene Brassylate 0.5 Disodium EDTA 0.4 Butylated Hydroxytoluene 0.3 Citric Acid 0.3

While described in terms of the presently preferred embodiments, it is to be understood that such disclosure is not to be interpreted as limiting. Various modifications and alterations will no doubt occur to one skilled in the art after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all such modifications and alterations as falling within the true spirit and scope of the invention. 

What is claimed is:
 1. A skin care composition comprising: (a) from about 0.001% to about 20% of a substituted diamine of structure I:

wherein R₁ is selected from the group consisting of cyclohexyl, phenyl, naphthyl, ortho-, meta- or para-substituted phenyl substituted with a moiety selected from the group consisting of: C₁-C₅ alkyl, C₁-C₅ alkoxy, halogens, and trifluoromethyl; a is 2 or 3; and R₃ and R₄ are independently selected from the group consisting of methyl and ethyl (b) a cosmetically acceptable carrier.
 2. The composition of claim 1, wherein a is 2, R₁ is selected from the group consisting of cyclohexyl, phenyl, naphthyl, ortho-, meta- and para-substituted phenyl with the following substituents: C₁-C₅ alkyl, C₁-C₅ alkoxy, halogens (F, Cl, Br), trifluoromethyl; and R₃ and R₄ are independently selected from methyl or ethyl, fused to form pyrrolidino.
 3. The composition of claim 1, wherein a is 2, R₁ is selected from ortho-, meta- or para-substituted phenyl, substituted with a moiety selected from the group consisting of, methyl, methoxy, Cl, F, CF₃, and fused phenyl; and R₃ and R₄ are both independently selected from methyl or ethyl.
 4. The composition of claim 1 further comprising an ingredient selected from the group consisting of alpha-hydroxy acids, beta-hydroxyacids, tyrosinase inhibitors, organic sunscreens, inorganic sunscreens, vitamins, retinol, retinyl esters, peptides, N-acetylglucosamines, anti-inflammatories, and anti-oxidants.
 5. The composition of claim 1 further comprising an additional skin lightening active selected from the group consisting of placental extract, lactic acid, niacinamide, arbutin, kojic acid, ferulic acid, hydroxyquinone, resorcinol and 4-substituted resorcinols.
 6. The composition of claim 1 further comprising an anti-perspirant active.
 7. The composition of claim 1 further comprising a surfactant. 